High energy milling powder preparation of equiatomic Ni-Ti shape memory alloy

A 50Ni50Ti at % powder mixture, by using commercially pure elemental powders, was prepared by mechanical alloying in an Attritor with the following conditions: the milling speed and the ball charge were 1500 rpm and 10:1 respectively. No process control agent was used in the processing.  The milling time was 1,2,4,8 and 16h, under a nitrogen atmosphere at room temperature. After milling it was determined the particle size distribution to determine the effect of milling time on powder particle size, the phases by X-ray diffractions (XRD) and the powder morphology by scanning electron microscopy (SEM). The high energy milling promotes dissolution of Titanium in Nickel and continuous amorphization by increasing the milling time. The powders after milling were compacted and heat treated at heat treated at 500, 650 and 800°C under vacuum microstructural evolution was characterized by X-ray diffractions (XRD). Different phases were detected in the heat treated samples showing the effect of temperature treatment and heterogeneity in the alloy.